Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/0003—Making bridge-work, inlays, implants or the like
  • A61C13/0004—Computer-assisted sizing or machining of dental prostheses
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/08—Artificial teeth; Making same
  • A61C13/083—Porcelain or ceramic teeth

Definitions

• This invention relates to a method of producing a dental restoration and, more particularly, to a method which employs CAD/CAM.
• Dental porcelains are typically comprised of a fine powder of "glass-like" particles, e.g., OptecTM porcelain powder sold by Jeneric/Pentron Incorporated (Wallingford, Connecticut).
• OptecTM porcelain powder sold by Jeneric/Pentron Incorporated (Wallingford, Connecticut).
• water or some suitable liquid is added to the powder.
• a wet, sandy mix is created which can be formed into desired shapes and then fused by heat to produce a solid substance similar to glass.
• porcelain may be enameled to metal or simply baked into a solid mass of pure porcelain.
• Restorations are usually fabricated on a replica or die of the prepared tooth. Materials may be added to the porcelain powders which improve color and strength.
• Another method of fabricating dental restorations is hot-pressing (high temperature injection molding). This technique is initiated by creating the restoration in wax.
• the wax pattern is lifted from the die and invested or surrounded by a mix of "plaster-like" material which is allowed to harden.
• a channel or opening leads from the outer surface of the investment into the wax pattern. Wax is eliminated from the investment during a burnout procedure.
• the dental porcelain provided in powder or pellet form, is placed in a special hot press and is melted and forced under pressure into the opening of the investment.
• porcelain pellets include soft-sintered OPC® pellets sold by Jeneric/Pentron Incorporated (Wallingford, Connecticut) and fully fused Empress® porcelain pellets sold by Ivoclar AG (Schaan, Liechtenstein).
• the melted material fills the void created by the wax pattern.
• the hardened ceramic is broken out of the investment. Where desired, color can be baked onto the surface of the restoration to simulate tooth color.
• Yet another method of fabricating dental restorations involves the computer-aided design, i.e., CAD/CAM, technique.
• CAD/CAM computer-aided design
• a 3-dimensional photo is taken of the stump of tooth over which a dental restoration is to be placed and of the teeth surrounding the stump.
• This photo is digitized and supplied to the CAD/CAM system, displaying the 3-dimensional picture on a viewing screen.
• the dental practitioner selects the most suitable tooth form from a plurality of tooth forms stored in the CAD/CAM system and projects the image of the selected tooth form over the stump until an optimum positioning and fit of the dental restoration is obtained.
• the digital data concerning the dental restoration thus formed are supplied to a numerically controlled milling machine operating in three dimensions, which precisely cuts a blank, i.e., a solid piece of metal or fully fused dental porcelain, on the basis of the digital data to provide the dental restoration.
• a method of making a dental restoration which comprises:
• soft-sintered dental porcelain pellet as utilized herein shall be understood to refer to a pellet that is formed by compressing at ambient temperature dental porcelain powder into a pellet (possessing any desired shape and configuration) and subsequently heating the pellet to a temperature which is sufficiently below the fusion temperature of the dental porcelain such that the density of the resulting soft-sintered pellet is less than about 85 percent, typically less than about 75 percent, of the theoretical density of the pellet.
• Such soft-sintered pellets possess a white, chalky appearance and are somewhat porous. This situation is to be contrasted with the case where the pellets are heated to a temperature which is at or close to the fusion temperature of the dental porcelain such that the density of the resulting sintered pellet is greater than about 90 percent of the theoretical density of the pellet.
• Such fully fused pellets possess a translucent, glossy appearance and exhibit very little, if any, porosity.
• teeth structure includes milled soft-sintered pellets possessing shapes which replicate natural teeth or are intended to be in association with natural teeth.
• dental restorations produced via the method of this invention exhibit significantly higher strength characteristics compared to dental restorations fabricated from fully fused pellets instead of soft-sintered pellets.
• CAD/CAM techniques and/or systems which can be utilized in the practice of this invention are not particularly limited and can include those described, for example, in U.S. Patent Nos. 4,575,805 and 4,663,720, the contents of which are incorporated by reference herein.
• An example of a commercially available CAD/CAM system which can advantageously be utilized in the practice of this invention is the PRO-CAMTM system available from IntraTech Dental Products (Dallas, Texas).
• the dental porcelain used to fabricate the soft-sintered pellet utilized herein is likewise not particularly limited.
• the dental porcelain is high strength OptecTM porcelain powder sold by Jeneric/Pentron Incorporated (Wallingford, Connecticut).
• OptecTM porcelain powder possesses a fusion temperature of about 1027°C.
• a suitable amount of powder is placed in a suitable pressing device, e.g., a Carver laboratory press, and compressed under pressure, e.g., 5000 psi, into a pellet at ambient temperature.
• the pellet is heated, e.g., in a conventional dental porcelain oven, to a temperature ranging from about 650 to about 925°C to soft-sinter the pellet.
• the resulting soft-sintered pellet possesses a density which is less than about 85, typically less than about 75, percent of the theoretical density of the pellet (as measured by Archimedes method).
• the soft-sintered pellet is a high strength OPC® porcelain pellet sold by Jeneric/Pentron Incorporated (Wallingford, Connecticut).
• OPC® porcelain pellets are sold in the soft-sintered form and thus can be readily used in the practice of this invention.
• OPC® porcelain pellets possess a fusion temperature of about 1150°C.
• the resulting tooth structure is invested with an investment refractory material.
• the investment refractory material selected depends on the composition of the soft-sintered pellet. It is well known in the art that the investment refractory material should not change dimension when heated to high temperatures.
• the refractory investment material possesses a coefficient of thermal expansion which is about 0.5 x 10 -6 /°C less than that of the soft-sintered dental porcelain pellet.
• OptecTM porcelain is employed in the method herein, it is preferred in the practice of the method herein to employ OptecTM Instant Refractory Material sold by Jeneric/Pentron Incorporated (Wallingford, Connecticut) as the investment refractory material.
• OptecTM Instant Refractory Material sold by Jeneric/Pentron Incorporated (Wallingford, Connecticut)
• OPC® soft-sintered porcelain pellets it is preferred to employ OPC® Instant Refractory Material sold by Jeneric/Pentron Incorporated (Wallingford, Connecticut) as the investment refractory material.
• the invested tooth structure is then fused by heating the pellet in a vacuum furnace to the fusion temperature of the soft-sintered pellet as is well known in the art.
• the investment material is removed from the fused tooth structure to provide a dental restoration which will precisely fit the tooth being restored and the surrounding teeth.
• veneering porcelain and/or stains may be subsequently placed on top of the outer surface of the resulting dental restoration utilizing techniques which are well known in the art.
• An OPC® soft-sintered dental porcelain pellet (available from Jeneric/Pentron, Inc., Wallingford, Connecticut) is machined into a tooth structure in partial shape or final shape using a PRO-CAMTM (trademark of IntraTech Dental Products Inc.) computer-assisted milling machine (available from Jeneric/Pentron Incorporated, Wallingford, Connecticut).
• the tooth structure is then invested with an investment refractory material (sold by Jeneric/Pentron Incorporated under the tradename OptecTM Instant Refractory material) which does not change dimension when exposed to high temperature.
• the invested tooth structure is fused by placing the sample in a conventional dental porcelain furnace at an initial temperature of 650° C and increasing the temperature to 1150° C at a heat-up rate of 55° C/min.
• the tooth structure is held at 1150° C for 30 seconds.
• the fully fused tooth structure is cleaned of the investment to provide a dental restoration which is prepared to receive a suitable veneering porcelain.
• the fully fused dental restoration has sufficient viscosity when re-heated to the maturing temperature of the veneering porcelain such that it does not lose its shape during the firing cycle of the veneering porcelain.
• the veneering porcelain forms a tight impervious surface necessary in the oral environment.
• OptimalTM porcelain (Jeneric/Pentron, Inc., Wallingford, Connecticut) is provided as a powder and is mixed with water or other suitable liquid to form a slurry.
• the slurry is applied to the dental restoration in accordance with well-known techniques and fused in a conventional dental porcelain furnace by heating the coated dental restoration from about 650° C to about 970° C at a heat-up rate of about 55° C/min. and holding at about 970° C for 30 seconds.
• the resultant coated dental porcelain restoration fits back into the original model.

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• Health & Medical Sciences (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Dentistry (AREA)
• Epidemiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Dental Prosthetics (AREA)
• Dental Preparations (AREA)

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Cited By (9)

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Citations (2)

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• 1996
  • 1996-08-16 US US08/699,149 patent/US5775912A/en not_active Expired - Lifetime
• 1997
  • 1997-03-11 DE DE69705780T patent/DE69705780T2/de not_active Expired - Lifetime
  • 1997-03-11 EP EP97420039A patent/EP0824897B1/de not_active Expired - Lifetime
  • 1997-03-11 ES ES97420039T patent/ES2162223T3/es not_active Expired - Lifetime
  • 1997-03-11 AT AT97420039T patent/ATE203386T1/de not_active IP Right Cessation
  • 1997-03-19 CA CA002200397A patent/CA2200397A1/en not_active Abandoned
  • 1997-08-15 JP JP22033897A patent/JP3254174B2/ja not_active Expired - Fee Related

Patent Citations (2)

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